Telecommunication service providers typically provide numerous voice and data services to end users (also referred to as subscribers of a telecommunication network). Some examples of voice services include voice calls, call forwarding, call waiting, etc. Some examples of data services include messaging, streaming audio/video, Voice over Internet Protocol (VoIP), online gaming, and IP-TV. The data services are managed by a packet core network of a telecommunications provider, which interfaces the end user with external Packet Data Networks (PDN), such as the Internet. Some examples of packet core networks include General Packet Radio Service (GPRS) core network, an Evolved Packet Core (EPC) of a Long Term Evolution (LTE) network, etc. Mobile devices, such as cell phones, personal data assistants, smart phones, notebook computers, etc., may access the voice or data services of a telecommunication network via an over the air interface with one or more base stations.
Telecommunication service providers use offline and online charging systems to keep track of the resource usage incurred by each subscriber user device of the telecommunication network. The 3GPP/3GPP2 standards groups have defined a set of specifications that may be used to implement online charging systems and offline charging systems in the various network domains (e.g., a circuit-switched domain, a packet-switched domain, and/or a wireless domain), IP multimedia subsystems, and emerging 3G/OMA application services.
As provided in 3GPP TS 32.240, offline charging is defined as a process where charging information for network resource usage is collected concurrently with the resource usage. The charging information is passed through a chain of charging functions, which results in the generation of Charging Data Record (CDR) files that are transferred to the network operator's Billing Domain for subscriber billing and/or inter-operator accounting. To implement offline charging, a Charging Trigger Function (CTF) is implemented in a subscriber's user device such as a cell-phone, tablet, or other suitable end user network element configured to request and provide services to a subscriber via the telecommunications network. The CTF collects information pertaining to chargeable events associated with various services provided by the telecommunications network to the subscriber's user device, assembles this information into matching charging events, and sends the charging events to a Charging Data Function (CDF), which is part of the telecommunication provider's Offline Charging System (OFCS).
The CDF receives the charging events from one or more CTFs, and uses the information included in the charging events to construct CDRs. A CDR is a formatted collection of information about a chargeable event (e.g., time of call set-up, duration of the call, amount of data transferred, etc.) for use in billing and accounting. The CDF then sends the CDRs to a Charging Gateway Function (CGF) of the OFCS. The CGF acts as a gateway between the network and the billing domain. Therefore, the CGF collects CDRs from the CDF (and other CDFs), optionally correlates the CDRs and writes the CDRs into a CDR file, and makes the CDR file available to the billing domain.
Various causes may result in a stoppage of the reporting of the charging events from a CTF to a CDF. The cause may be a temporary problem, such as an intermittent communication problem between the subscriber's device or other network element and a base station interconnected with the telecommunication service provider's core network, or a more serious state-related problem, such as one which may result in a shutdown and subsequent reboot or restart of a network element implementing the CTF. The former communication problems are often resolved quickly, as the telecommunication network is monitored in real-time and telecommunication operators provide sufficient means for alternative path selection. However, the latter case which indicates an unanticipated restart or reboot of the CTF, remains an issue which causes significant processing strain on the resources of an OFCS in processing session (or event) accounting records.